Rod-shaped filter element



April 5, 1960 P. A, MUELLER 2,931,364

ROD-SHAPED FILTER ELEMENT Original Filed April 18. 1955 Fig.2 Fig.3 Fi .4 Fi .5 Fi .5 Fi .7 Fig.8

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Paw Hwy/702a? KGB-SHAPED FETER ELEMENT Paul Adoif Mueller, fiosenhugel, Herrliberg, Switzerland firi' inai application April 18, 1955, Serial No. 532,085, new Patent No. 2,820,461, dated January 21, 1958. Divided and this application November 22, 1957, Serial No. 658,251

1 Claim. (Cl. 131-208) The present invention relates to the continuous production of tobacco filters, particularly for use in cigarettes.

This application is a division of copending US. patent application Serial No. 502,085, filed April 18, 1955, now matured into U.S. Patent No. 2,820,461.

One of the important properties which are required for a smoke filter of the aforesaid type, is primarily high absorption in order to diminish any harmful substances in the tobacco smoke without markedly or considerably reducing the porosity of the filter.

By way of example, the filters used at present for cigarettes consist of a multi-layer or crimped paper web, e.g. multi-layer crimped tissue paper, crimped cellulose wedding, rolled together in longitudinal direction of the filter, with or without intermediate layers of adsorptive materials, e.g., thin strips of wadding inserted between the separate layers of paper. The disadvantages of such filters is that they have pronounced longitudinal ducts through which the smoke can pass unhindered, i.e., unfiltered. To eliminate this disadvantage, the suggestion has already been made to arrange a ball of Wadding in front of such a filter at the tobacco side, which ball has the task of absorbing the mentioned harmful substances so that the actual filter which follows has only a subordinate importance. However, even such a combined filter is no solution for the problem, apart from the fact that its production is complicated and therefore expensive.

Other cigarette filter inserts made of sponge, wool, wood fibre, fibers twisted together to form a cord, knitted fabrics, fiat metal wires and textile fibers, strands of Wadding running lengthwise of the tobacco fibers, a compound of filter paper, etc., have not been generally accepted because either their filtering effect was not technicaliy satisfactory, they were too expensive or were ditficult to incorporate in the cigarettes.

Even the addition of adsorption substances, such as activated carbon, yields no satisfactory improvement because these adsorption substances become partly loose during smoking and are inhaled together with said harmful substances.

Attempts to achieve a greater filtering eflz'ect with the aid of chemical agents have not led to a satisfactory result either, because in tobacco the nicotine is not in its basic form, i.e. cannot be bound with acid, but is distilled ofi in the form of colloid salt with the aqueous vapor produced by the moist tobacco. Such colloid salts can only be bound by physical adsorption, for which silica gel and activated carbon are suggested. Silica gel, however, is out of the question because it effects, in essence, only a binding of the water, whereby the smoke is, to be sure, dried but not purified of its harmful substances. True, activated carbon does not have this drawback, but it fails in practice because it is not possible to mix activated carbon with the cigarette tobacco or, for instance, thewadding. or to press activated carbon together with the wadding to form a filter, as no method of binding it nite States Patent F 2,931,364 Patented Apr. 5, 1960 to a carrier so that it will resist rubbing, has yet been found.

The filtering action, i.e. the separation of nicotine, tar products and other harmful constituents of the smoke, depends mainly on the surfaces brushed or contacted by the smoke during its passage through the filter.

Furthermore, it has already been attempted to produce filters from fibre strands made, by way of example, from acetate silk or cotton wadding. Filters made of pure fibrous material webs, e.g. of acetate or wadding strands, cannot, however, be processed without additional stiffening agents as they have inadequate crushing and compression strength. If, however, a cylindrical smoke filter is so tightly packed with fibres that the fibres own elasticity gives sufl'icient strength to the filter, then the latters porosity is too low, i.e. its tensile resistance is too high. It has already been attempted to eliminate this defect by spraying the fibre strands, before molding them to form a filter, with chemical agents so as to produce a fibrous framework which is less dense but is stifiened by a plurality of points of mutual adhesion and which has the desired strength. It has, however, been shown that all the known, suitable binding agents, which have an adequate adhesive efiect but do not reduce porosity by an inadmissible amount, contain more or less harmful constituents and are not completely odorless.

Finally, an attempt has already been made to produce suitable filters from strips of paper which have dimensions similar to those of tobacco fibres and should be capable of being processed, if normal cigarette machines are used. Here, too, however, it has been shown that a filter of the desired strength, capable of being processed and ofiering adequate resistance to the pressure of the lips during smoking, has an inadmissibly high tensile resistance.

The present invention aims at producing smoke filtering members Whose efiective total surface is greater than that of all paper and fibre strand filters known hitherto, without, however, the tensile resistance, with filters made of paper, being inadmissibly high, while with filters made from fibre strands the tensile resistance can be reduced without the necessity of strengthening the fibrous framework by the addition of binding agents.

The present invention contemplates a tobacco filter particularly suitable for cigarettes, and provides means contributing to a filtering member which contains at least a few elongated vortical and condensation strips which are made of a flexible flat material and in which at least one side or elongated surface is provided with'irregularities so as to enlarge the surface area.

It is another object of the invention to provide means affording improved filter properties for cigarettes and like tobacco products without substantially increasing the production cost thereof.

These and other objects of the invention will become further apparent from the following detailed description, reference being made to the accompanying drawings, showing preferred embodiments of the invention.

In the drawings:

Fig. 1 shows the principle of the invention according to which filter strips are arranged, and illustrates the same diagrammatically (the materials located between the strips being omitted);

Figs. 2 to 8 are each a plan view of a typical embodiment of a vortical and condensation strip;

Fig. 9 is a cross-section through vortical and condensation strip.

The results of research show that the absorption of nicotine and tar products from the tobacco smoke can be substantially increased if said smoke passes along elongated narrow strips of flat material which is perforated,

, stampedor similarly provided with an irregular surface.

. 3 in a :filter consisting of such strips .of fiat material the surface contacted by the smoke as it flows through the smoking article must necessarily be larger than in the case of a vertical filter which consists of strips of a material which are similar'but not provided with surfaceirregularities. These irregularities, in particular, if they have a sharp-edged or frayed structure, provide, moreover, a plurality of obstacles in the flow path of the smoke, which obstacles result in labyrinthine paths offlow and produce a plurality of randomly distributed vortex centres in the flow of the smoke. In this way the separation of solid and liquid particles from the tobacco smoke is substantially increased.

Furthermore, it has been shown that a condensation effect can be achieved with such vortical strips, parties ularly when the latter consist ofvmetallized paper or metal foils. The vortical strips always have a lower temperature than the smoke brushing past them so that the vaporous constituents of the smoke are to a large extent condensed and deposited on the surfaces, of the strips.

. si l-era .tively, a beingalsc possible to combine/the embodiment according to Fig. 4 or 5 with that according to Fig. 2 or 3, as is shown in Fig. 6. Semi-circular lateral indentations 13, as shown in Fig. 7, are also advantageous, possibly combined with round holes according to Fig. 3 in Fig. 8.

Other usable forms of strips are producedby stamping the appurtenant mammillated material, for instance, in the manner illustrated in longitudinal section in Fig. 9, which produces a substantially flat strip material 2. provided with evenly distributed humps 14. Here, too, the result is an enlarged surface area with obstacles to flow which favor the formation of vortex centres, particularly if the humps 14 are sharp-edged.

Finally, it should also be pointed out that it is possible to enlarge the surface area of some fiat strip materials by roughening same.

It is suitable to use for the vortical and condensation strips aflat material consisting of'fibrous substances, for

'Asa result of the not inconsiderablethermal capacity ofthese vortical and condensation strips, they are only slightly heated by the smoke at normal smoking speed. If a filter is constructed from a combination of such vortical and condensation strips together withabsorbent fibrous materials such as cotton or cellulose wadding, an

optimum filtering effect can be achieved by means of the simultaneous absorption and adsorption which occur.

In a filter constructed of fibrous materials together with vortical and condensation strips the latter, particularly if theyconsist of relatively strong material such as blotting paper or metal foils, also contribute substantially to the strengthening of the filten. Thus, the suitablefibrous materials can then be chosen without regard to their strength and only with regard to the best filtering effect, which has not previously been possible, and the requisite strength of the filter can be ensured by means of a suitable frameworkof vortical and condensation strips.

The rigid framework made of such vortical and con-. densation strips which contribute quite substantially toward a good filtering effect also enables, however, fibrous materials to be replaced or supplemented by other absorbent materials, such as plastic foam flakes, sponge flakes, viscose foam, etc., the use of which has hitherto led to difficulties owing to their strength being'as a rule inadequate.

=In tests on filters of the present design, with vortical and condensation strips, it has been discovered that the separation efiect in respect of the harmful constituents of the tobacco smoke is only about 50 percent better than with filters made of the same'material but without the strips provided with enlarged surface areas. The tensile resistance, however, is substantially less and thestrength of the filter enables it to be mechanically processed without ditliculty.

The basic arrangement of a preferred type vortical or twisted strips inside a filter is shown diagrammatically in Fig; 1. In the outer sheath 1, which consists, for iiistance, of tissue paper (shown in dotand' dash lines), there is disposed a plurality of vortical and condensation strips 2, the filter preferably constituting an endless, elongated rod formation from which the individual filter plugs are cut ofi to the desired length. Accordingly, the strips 2 may form endless webs which extend along the filter sheath 1 and are combined to form an elongated bundle of strips which are in a randomly chosen position in relation to each other.

Various forms of perforations or other patterns for enlarging or increasing the surface area may be provided for the strips. By way ofexample, Figs. 2 and 3 show round andoblong holes or rents 9 and 10, respectively, in a vortical and condensation strip 2. The lateral indentations may also have a rounded or randomly frayed configuration 11 or 12, as shown in Figs. 4 and amp instance, absorbent paper or stiffened fleece made from natural or synthetic fibres. Also usable are strips of woven fabric, as well as those made of foil-like, heatresistant, tasteless and odorless plastics. Compressed plastic foam, with and without surface coating, can be used provided it meets the hygienic requirements. If particular importance is attached to a good condensation effect, it is'advisable to use a flat material which has on at least one side a metallic surface whichmay be compact or disconnected. By way of example, paper metallized on one or both sides can be used for this purpose,

as can thin metal foil made of aluminum and other suitable metals. 7

. Filters according to the present invention may, for instance, contain exclusively vortical and condensation strips of the type described.

As already mentioned, the combination of vortical and condensation stripswith fibrous materials is particularly advantageous 'The fibrous material 20 indicated in Fig. l which is bydrophylic may be'of natural origin, such as cellulose fibres, cotton wadding, etc;, or of synthetic origin, such as rayon, acetate viscose fibres.

The multi-layer strip formation may be covered with fibres and perforated to result in filters which have a larger content of strips and a smaller content of fibrous material (see Fig. 1) than other filters.

In place of the fibrous materials, or in combination with'th'em, randomly distributed flakes of sponge or foamlike material can also be provided in the filter inside the vortical and condensation strips. Suitable for this purpose is plastic foam'having hollow spaces which intercommunicate at least in part and are made, for instance, of carbamide resin. Foam or sponge-like compomds made from viscose lamellae, latex foam, neoprene foam, etc., are also suitable.

It can thus be seen that there has been provided according to the present invention a filter for a tobacco smoking article which consists of a rod-shaped filter element provided with a plurality of strips, each strip being substantially coextensive in length with that of said rod-shaped filter element and being slightly twisted aboutv its axis and about adjacent strips, said strips being haphazardly arranged in elongated bundle formation and consisting at least partly of flexible absorbent material. Each strip possesses a surface configuration, which is worked upon, preshaped or distended to thereby enlarge the filtering surface area. Hydrophilic cellulose fibers of relatively small dimensions miy be interspersed betweensaid strips in random fashion to thereby provide a tortuous path for the smoke to follow when travelling through said filter element, said filter element having a sheath surrounding and maintaining said filter element in its rod-shaped form.

vention and it is intended that such obvious changes and modifications be embraced by the annexed claim.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

A tobacco filter comprising a rod-shaped filter element including a plurality of strips of fibrous sheet material arranged in elongated bundle formation, each of said strips having a longitudinal axis, being substantially coextensive in length with that of said filter element and being at least slightly twisted about the longitudinal axis and about adjacent strips, said strips being made of at least partially flexible absorbent material with at least one surface preshaped so as to present an irregular surface area to tobacco smoke, which surface area is relatively larger than that of a perfectly smooth surface area, at least some of said strips being provided with at least one frayed lateral edge and with rents disposed longitudinally of the respective strips.

References Cited in the file of this patent UNITED STATES PATENTS Bourgeois Dec. 19, Segal Mar. 10, Aivaz Dec. 15, Carlson Mar. 26, Davidson June 4, Nicol Oct. 7, Schur et a1. Aug. 6, Muller Jan. 21,

FOREIGN PATENTS Germany Jan. 25, Switzerland Jan. 4, Great Britain Sept. 6, Great Britain July 5, 

